Is it possible to implement a graphical interface using CALayer in an iOS app?

Yes, it is possible to implement a graphical interface in an iOS application using CALayer, but with some caveats.

CALayer is a low-level class responsible for displaying and animating content. It is not designed for handling user events or managing interface elements like UIView.

Therefore:

• You can create and configure CALayer objects for displaying graphics, animations, shadows, borders, etc.
• For a full interface with touch handling and interaction, it is better to use UIView, which contains and manages CALayer.

Example of using CALayer to add a shadow to a UIView:

let view = UIView(frame: CGRect(x: 50, y: 50, width: 100, height: 100))
view.backgroundColor = .red

view.layer.shadowColor = UIColor.black.cgColor
view.layer.shadowOpacity = 0.5
view.layer.shadowOffset = CGSize(width: 5, height: 5)
view.layer.shadowRadius = 10

Thus, CALayer is a powerful visualization tool, but for creating a complete graphical interface, UIView and its subclasses are usually used.